The present invention relates to an arrangement for changing a machining program in a numerical control machine tool having an override command means such as an override switch.
Usually, when the spindle rotation speed or feed speed set in the machining program for a numerical control machine does not meet the demand, the operator manipulates the override command means such as an override switch to obtain optimum spindle rotation speed or feed speed for the demanded cutting condition. In addition, when a machining cycle includes a plurality of steps which are to be performed by different tools, it is necessary to adjust the spindle rotation speed or the feed speed for each of these steps performed by respective tools.
Hitherto, however, the adjustment of speed effected through the override switch is merely to change the speed set by the machining program, and is not to amend the program itself. Therefore, in a machining operation in which a machining cycle consisting of a plurality of steps is repeatedly executed, the operator is obliged to repeatedly adjust the speed at each time the new step is commenced in each of the repetitional machining cycles. Such frequent adjustment is extremely troublesome and tends to incur erroneous operation.